Two special cell types in the nose have been identified as possible initial infection sites of COVID-19 coronavirus. Scientists have found that goblet cells and ciliated cells in the nose contain large amounts of proteins that SARS-CoV-2 virus uses to enter our cells. As part of the human cell map (HCA) “lung biological network”, researchers and their collaborators from the Wellcome Sanger Institute, the University of Groningen Medical Center and the French National Academy of Sciences, the identification of these cells may help explain the high transmission rate of COVID-19.
The article, recently published in the journal Nature Medicine, is the first published by the Lung Biology Network as part of an ongoing international effort to use human cell map data to understand infection and disease. This further suggests that cells in the eyes and other organs also contain viral invasion proteins. The study also predicted how other immune system genes regulate a key protein and revealed potential targets for therapeutic development that reduces transmission.
Novel coronavirus’s disease-COVID-19 affects the lungs and respiratory tract. Patients may have symptoms similar to influenza, including fever, cough and sore throat, while some people may be asymptomatic but still have infectious viruses. In the worst cases, the virus can cause pneumonia and eventually death. The virus is thought to be spread by droplets produced when an infected person coughs or sneezes and seems to spread easily in affected areas. So far, the virus has spread to more than 184 countries, killing more than 180000 people.
Scientists around the world are trying to understand exactly how the virus spreads to help prevent transmission and develop vaccines. Although the virus known to cause COVID-19 disease, the coronavirus associated with SARS-CoV-2, and the SARS epidemic in 2003, uses a similar mechanism to infect our cells, the exact cell type involved in the nose has not been determined before.
To find out which cells may be involved in the transmission of COVID-19, the researchers analyzed single-cell RNA sequencing data sets of multiple human cell profiles of (HCA) from different tissues of more than 20 uninfected people. These cells include cells from the lungs, nasal passages, eyes, intestines, heart, kidneys and liver. The researchers looked for which cell simultaneously expressed two key entry proteins that the COVID-19 virus uses to infect the cell.
Dr Waradon Sungnak, from the Wellcome Sanger Institute and lead author of the paper, said: “We found that the TMPRSS2 protease and receptor protein ACE2, which activates SARS-CoV-2 entry, is expressed in cells in different organs, including cells in the inner wall of the nose. We found that the contents of these two COVID-19 virus-related proteins in goblet cells and ciliated cells produced by nasal mucosa were the highest among all cells in the airway. This makes these cells the most likely initial route of infection for the virus. ”
Dr Martijn Nawijn, from the University of Groningen Medical Center in the Netherlands, said on behalf of the HCA Lung Biology Network: “this is the first time that these special cells in the nose have been found to be associated with COVID-19. Although there are many factors that contribute to the spread of the virus, our findings are consistent with the rapid infection rate seen so far. The location of these cells on the inner surface of the nose makes them vulnerable to the virus and may also help spread to other people. ”
These two key entry proteins ACE2 and TMPRSS2 are also found in the cells of the cornea and the inner wall of the intestine. This suggests that another possible route of infection is through the eyes and lacrimal glands, as well as the possibility of fecal-oral transmission.
When cells are damaged or fight infection, various immune genes are activated. Studies have shown that the production of ACE2 receptors in nasal cells may be initiated at the same time as other immune genes.
The Global HCA Lung Biology Network will continue to analyze data to further understand the cells and targets that may be involved in COVID-19 and to link them to patient characteristics.
Professor Jeremy Farrar, director of Wellcome Sanger, said: “By pinpointing the exact characteristics of each cell type, the human cell map is helping scientists diagnose, monitor and treat diseases, including COVID-19, in an entirely new way. Researchers around the world are working at an unprecedented rate to deepen our understanding of COVID-19, and this new study proves it. Cross-border cooperation and public sharing of research are essential for the rapid development of effective diagnoses, treatments and vaccines to ensure that no country is left behind. ”
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